Single parents can join the National Guard but not the active duty military forces, according to a September 2009 article in "The New York Times." The reason you can join the Guard is that positions are part-time as opposed to full-time as with active duty branches. You do have to provide a family care plan when you apply so the Guard command knows that you can effectively balance parenting responsibilities and job commitments.
Single Parent Challenges
Even though you can apply to the National Guard as a single parent, it is important to understand the challenges you face. Upon enlisting, you spend 10 weeks in basic training and up to 64 weeks in advanced training before returning home. At that point, you can return home to a regular job and life. You must also participate in Guard training one weekend each month and two full weeks in a year. You must consider how you will juggle these commitments with your duties as a single parent.